Insulin resistance is important in the development of adult-onset diabetes mellitus and several lines of evidence indicate that an initial defect in adult onset diabetes is reduced insulin-stimulated recruitment of GLUT4 glucose transporter from a sequestered intracellular site to the cell surface in muscle and fat cells. An increase in cell surface (plasma membrane) GLUT4 amount allows for an increased rate of facilitated diffusion of glucose into cells. Presently available methods of determining or measuring GLUT4 translocation, such as methods involving assessment of .sup.3 H 2-deoxyglucose uptake, cell fractionation, counting radioactivity that binds to adherent cells on a multiwell plate, plasma membrane sheet assays and immunofluorescence microscopy are laborious and/or only semiquantitative. It would be of considerable interest to be able to measure GLUT4 glucose transporter protein translocation easily and quantitatively.